Enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 strain is a human enteric bacterial pathogen that causes diarrheal disease, hemorrhagic colitis, and hemolytic uremic syndrome (HUS). Each year in the United States, an estimated 20,000 people suffer from diarrheal disease associated with E. coli O157:H7 infection, which is typically contracted by ingesting contaminated foods, especially undercooked meat. Approximately 6% of infected individuals develop HUS, which can lead to renal failure and death. Young children and the elderly are particularly susceptible to developing HUS.
In general, bacterial infections are commonly treated by administering appropriate antibiotics. However, E. coli O157:H7 infection typically has a very rapid progression, and is consequently very difficult to treat. Often by the time the disease is diagnosed, the infected individual is severely ill and toxic proteins secreted by the bacteria may have damaged mucosal cells and entered the blood stream. Antibiotic treatment of patients infected with E. coli O157:H7 is generally not successful, and is now believed to be contraindicated.
E. coli O157:H7 bacteria are very proficient at establishing an infection; ingestion of as few as 10 live bacteria is sufficient to establish an infection. The highly infective nature of E. coli O157:H7 and the devastating sequelae associated with infection by this bacteria, together with the extensive public attention given to outbreaks of hemorrhagic colitis, has generated a great deal of interest among medical professionals and the general public in developing the means for early diagnosis and treatment of the disease. The entire genome of the E. coli O157:H7 EDL933W (ATCC 43895) was sequenced with the expectation that valuable information concerning the organism's pathogenicity would be uncovered, which may facilitate development of methods of preventing infections, or preventing or treating hemolytic uremic syndrome in individuals infected with of the organism. The DNA sequence of E. coli O157:H7 was compared with that of E. coli K12, a non-pathogenic strain commonly used in research. The genome of E. coli O157:H7 exceeds that of E. coli K-12 by more than a million base pairs and has up to 1000 genes not found on K-12. These additional gene sequences are distributed throughout more than 250 sites in islands, with each island containing from zero to sixty genes (1).
What is needed in the art is an improved understanding of factors involved in the pathogenesis of E. coli O157:H7, and methods for preventing or treating hemolytic uremic syndrome in individuals infected with E. coli O157:H7. What is also needed in the art is an understanding of factors responsible for enteric disease that are common to pathogenic E. coli. 